High purity gas delivery systems, such as those used in semiconductor manufacturing or other thin film coating processes, typically include a source of high purity gas coupled to a process chamber through a series of gas distribution and control components, such as a mass flow controller, one or more pressure sensors and/or regulators, a heater, one or more filters or purifiers, and shutoff valves. A pump is used to pump each gas from its source to the process chamber.
Some processes must be performed at very low pressures (high vacuums), e.g., a pressure on the order of one torr or less. One ultra-high vacuum system adapted to operate at low conductances includes a turbo pump, and a pendulum or gate valve for controlling the pressure created by the turbo pump within a predetermined range so as to allow very precise control of the mass of the gas flowing to the process chamber. Such systems typically utilize a turbo pump and a combination of valves connected together with gas tubing and suitable connectors so as to provide a closed system as well as careful control of pressure when the pendulum valve is near the closed and sealed position, where pressure control is more difficult.
As the dimensions of semiconductor devices decrease and their densities increase, semiconductor manufacturing processes have become increasingly intolerant of particulate contamination. One important source of such contamination is the gases used during the process, and particularly particulates carried by the wetted surfaces in the passageways through which the gases are delivered from the source to the chamber. Moisture or dust which accumulates within these passageways are carried with the source gas and deposit onto the semiconductor devices being processed, creating defects. Moisture also may corrode the wetted surfaces, leading to flaking of particles from these surfaces. The passageways of the turbo pump, the combination of valves and the connecting tubing and connectors can thus be a source of contaminants.
To reduce contamination of this sort, gas processing components used in manufacturing semiconductor devices are usually made in low-dust, low-moisture environments, and purged for lengthy periods of time at elevated pressures after manufacture. The components are then typically packaged and sealed in pressurized nitrogen for shipment. As a result, the interior of the component is exposed only to the clean room environment in which the semiconductor processing equipment is located, and only for the brief period of time between removal of the packaging and sealing of the component into the processing equipment. In addition, the total path length, or "footprint" of the flow of the gas should be as short as possible to minimize the wetted surface area to which the gas is exposed.